Technical data

SINAUT MD720-3
C79000-G8900-C210
59
Glossary
DynamicDNS
providers
offer the capability of
being accessible via a
fixed Internet address
Each computer which is connected to the Internet has an IP address
(IP = Internet Protocol). An IP address consists of 4 numbers,
separated by full stops, which each have up to three digits. If the
computer is online via the telephone line per modem, per ISDN or per
ADSL it is assigned a dynamic IP address by the Internet service
provider, i.e. the address changes from session to session. Even if
the computer is online for 24 hours without interruptions (e.g. with a
flat rate) the IP address is changed from time to time.
If a local computer is to be accessible via the Internet it must have an
address which is known to the remote communication partner. Only in
this way can the communication partner establish a connection to the
local computer. However, if the address of the local computer
continually changes this is not possible, except where the operator of
the local computer has an account with a DynamicDNS provider
(DNS = Domain Name Server).
He can then define a name in URL format (URL = Uniform Resource
Locator) with this provider under which the computer shall be
accessible in the future, e.g. www.xyz.abc.de. In addition the
DynamicDNS provider provides a small program which has to be
installed and executed in the computer in question. In each Internet
session of the local computer this tool informs the DynamicDNS
provider of the computer's current IP address. Its domain name
server registers the current assignment of URL  IP address and
advises this to other domain name servers in the Internet.
If a remote computer now wishes to establish a connection to the
local computer which is registered with the DynamicDNS provider the
following takes place: The remote computer uses the URL (= host
name) of the local computer as the address. This results in a
connection being established to the responsible DNS (Domain Name
Server) to determine the IP address currently assigned to this URL.
The IP address is transferred back to the remote computer which now
uses it as the destination address. This now leads to exactly the
desired local computer.
This procedure is the basis for all Internet addresses in URL format:
First a connection is established to the DNS to determine the IP
address assigned to this URL. Once that has happened this "looked-
up" IP address is used to establish the connection to the desired
communication partner, i.e. to any Internet site.
You can find DynamicDNS providers on the Internet under the
following address: http://netzadmin.org/ddns-provider.php